Impact of hydrological conditions on the radiocarbon reservoir effect in lake sediment 14C dating: the case of Kusai Lake on the northern Qinghai-Tibet Plateau

doi:10.1016/j.quageo.2020.101149

Quaternary Geochronology

Volume 62, March 2021, 101149

https://doi.org/10.1016/j.quageo.2020.101149 Get rights and content

Abstract

The hydrological conditions of a lake system strongly influence the reservoir effect in the radiocarbon dating of endogenic organic and inorganic carbon in lake sediments. In this paper, we compare ¹⁴C dating with varve counting results for cores from Kusai Lake to determine the temporal changes in ¹⁴C reservoir ages during the last 2000 years. Based on the ¹⁴C budget equation for a lake system, the characteristics of geomorphology, topography, and river systems in the catchment, and the physical and chemical properties of modern water in Kusai Lake, the hydrological conditions and the reservoir effect age are discussed. The reservoir age of the sediment core from northwestern Kusai Lake (i.e., deep water area) fluctuates slightly between 2980 and 3310 years, while that from southeastern Kusai Lake (i.e., shallow water area) fluctuates greatly between 3130 and 4010 years. Under the relatively steady conditions of atmospheric ¹⁴C levels for the past 2000 years, the ¹⁴C level in the dissolved inorganic carbon (DIC) of Kusai Lake is mainly related to carbon influxes from river and glacial meltwater and carbon outfluxes in lake water. The water in the shallow water area is more affected by the Kusai River, glacier meltwater, and lake outflow than the water in the deep water area, which has caused larger temporal changes in the radiocarbon reservoir ages in the shallow water area than in the deep water area during the last 2000 years.

Introduction

As lake sediments record continuous deposition at a high resolution, they have become one of the best archives for palaeoclimate reconstructions (Shen et al., 2010; Wang and Zhang, 1999). There are many lakes distributed on the Qinghai-Tibet Plateau and in Inner Mongolia and Xinjiang in China (Wang and Dou, 1998; Yang et al., 2010). Many palaeoclimate records have been obtained recently from lake sediments in these three regions (Chen et al., 2019; Feng et al., 2005; Herzschuh, 2006; Shi, 2002; Wang et al., 2010a; Zhao et al., 2009). However, as these lakes are located in arid and semi-arid areas, finding terrestrial plant macrofossils or charcoal particles in lake sediments is difficult. As a result, autochthonous total organic carbon (TOC) or aquatic plant macrofossils are used for accelerator mass spectrometry (AMS) ¹⁴C dating, which is susceptible to the radiocarbon reservoir effect that makes the measured ¹⁴C age older than the actual age (Deevey et al., 1954; Godwin, 1969). The radiocarbon reservoir age is usually determined by linearly extrapolating the downcore ¹⁴C age-depth relationship to the surface sediment (Fontes et al., 1996; Gyawali et al., 2019; Hou et al., 2012; Liu et al., 2009) or directly measuring the ¹⁴C age of lake surface sediments (Fontes et al., 1993; Henderson et al., 2010; Herzschuh et al., 2006; Hou et al., 2012). Then, based on the assumption that the hydrological conditions of the lake did not change and the radiocarbon reservoir age was constant during geological history, reservoir-corrected ¹⁴C ages are obtained by subtracting a constant radiocarbon reservoir age from all measured downcore ¹⁴C ages. Apparently, these methods ignore radiocarbon reservoir age variations with time, which can cause uncertainty in the age model. To estimate the reliability of the chronological sequence, some studies have explored the influence of hydrological conditions on the radiocarbon reservoir effect in the measured ¹⁴C age of lake sediments (Stiller et al., 2001; Wang et al., 2010b; Yu et al., 2007; Zhou et al., 2009). Varves are well preserved in the sediments of Kusai Lake, which is located in the Hoh Xil region of the Qinghai-Tibet Plateau (Chen, 2017; Jia and Liu, 2019; Liu et al., 2014). Previous studies have shown that the ¹⁴C reservoir age is approximately 3200 years in Kusai Lake (Jia and Liu, 2019; Liu et al., 2009, 2014). In this paper, we compare AMS ¹⁴C dating with varve counting results for cores from Kusai Lake to determine the radiocarbon reservoir age variations with time during the last 2000 years. The geomorphology, topography, and river systems of the catchment and the modern physical and chemical properties of Kusai Lake are discussed to explore the hydrological conditions in Kusai Lake and their influences on the reservoir effect age.

Section snippets

Study area

Kusai Lake (35°37′-35°50′ N, 93°38′-93°15′ E, 4475 m a.s.l) is located in the northeastern Hoh Xil region of the Qinghai-Tibet Plateau (Fig. 1A). The Kusai Lake basin is a secondary depression in a Meso-Cenozoic intermontane fault basin controlled by major tectonic lines that are oriented northwest to southeast (Zheng et al., 2002). Many lakes, such as Zhuonai Lake, Kusai Lake, Haidingnuoer Lake, and Salt Lake, are distributed along the major tectonic lines (Jing et al., 2014; Zheng et al., 2002

Sample collection

Using a UWITEC platform (Austria), we drilled a sediment core with a length of 1.52 m (KSD-1) in the northwestern part of Lake Kusai at a water depth of 49.8 m in September 2010 and sediment cores with lengths of 3.64 m (KSS-2010) and 5.0 m (KSS-2015) from the southeastern part of Kusai Lake at a water depth of 14.5 m in September 2010 and 2015, respectively. A YSI Multiparameter Water Quality Sonde (America) was used to measure the changes in water temperature and salinity at 1 m intervals

Chronology

The varve counting, ²¹⁰Pb–¹³⁷Cs dating, and ¹⁴C dating results of cores KSD-1 and KSS-1 show that the lake sediments of Kusai Lake are annually laminated (varved) (Chen, 2017; Liu et al., 2014; Jia and Liu, 2019). The varved sediments in Kusai Lake are formed by the alternating deposition of aeolian material on ice during winter and thin layers of materials such as biological debris and authigenic carbonate precipitation during summer (Chen, 2017; Chen and Liu, 2016; Chen et al., 2016; Liu et

Components of the ¹⁴C budget in Kusai Lake

The dissolved inorganic carbon (DIC) in lake water is the source of endogenic organic and inorganic carbon. As the DIC does not achieve isotopic equilibrium with atmospheric CO₂ in many lakes, the apparent ¹⁴C ages of autochthonous organic carbon, aquatic plants, and endogenic carbonate in lake sediments are higher than their true ages. The initial radiocarbon specific activity of DIC in lake water depends on the atmospheric level of ¹⁴C and hydrological conditions, so calculating and

Conclusion

The water in the shallow water area is more influenced by the Kusai River, glacier meltwater, and the outflow of lake water than the water in the deep water area of Kusai Lake. This feature can also be seen from the fact that the temperature and salinity values of modern lake water in the deep water area are more stable than those in the shallow water area of Kusai Lake.

The ¹⁴C budget balance of Kusai Lake is generally affected by carbon influxes in river and glacial meltwater and carbon

Declaration of competing interest

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work” Impact of hydrological conditions on the radiocarbon reservoir effect in lake sediment 14C dating: the case of Kusai Lake on the northern Qinghai-Tibet Plateau” submitted.

Acknowledgements

This study was supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP), Grant No. 2019QZKK0202.

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Impact of hydrological conditions on the radiocarbon reservoir effect in lake sediment 14C dating: the case of Kusai Lake on the northern Qinghai-Tibet Plateau

Abstract

Introduction

Section snippets

Study area

Sample collection

Chronology

Components of the 14C budget in Kusai Lake

Conclusion

Declaration of competing interest

Acknowledgements

Luminescence chronology and radiocarbon reservoir age determination of lacustrine sediments from the Heihai Lake, NE Qinghai-Tibetan Plateau and its paleoclimate Implications

J. Earth Sci.

Westerlies Asia and monsoonal Asia: spatiotemporal differences in climate change and possible mechanisms on decadal to sub-orbital timescales

Earth Sci. Rev.

Reconfirmation and Formation Mechanism of Var Ved Lake Sediments from Lake Kusai in the Hoh Xil Area, Northern Tibetan Plateau, College of Resources Environment and Tourism

Surface textural analysis of quartz grains from varved sediments of Lake Kusai in the Hoh Xil area, Tibetan Plateau

J. Lake Sci.

Micro area analysis and mechanism of varves from lake Kusai in the Hoh Xil area, northern Tibetan plateau

Acta Geol. Sin.

The natural 14C contents of materials from hard-water lakes

Natl. Acad. Sci.

Dynamic change and cause analysis of Salt Lake area in Hoh Xil on Qinghai-Tibet Plateau during 1976 - 2017

J. Glaciol. Geocryol.

Lacustrine and eolian records of Holocene climate changes in the Mongolian Plateau: preliminary results

Quat. Int.

Holocene environmental changes in Lake Bangong basin (Western Tibet). Part 1: chronology and stable isotopes of carbonates of a Holocene lacustrine core

Palaeogeogr. Palaeoclimatol. Palaeoecol.

Stable isotope and radiocarbon balances of two Tibetan lakes (Sumxi Co, Longmu Co) from 13,000 BP

Quat. Sci. Rev.

The value of plant materials for radiocarbon dating

Am. J. Bot.

Temporal changes of the 14C reservoir effect in lakes

Radiocarbon

Paleo-environmental change since the Late Glacial inferred from lacustrine sediment in Selin Co, central Tibet

Palaeogeogr. Palaeoclimatol. Palaeoecol.

Late Holocene isotope hydrology of Lake Qinghai, NE Tibetan Plateau: effective moisture variability and atmospheric circulation changes

Quat. Sci. Rev.

Palaeo-moisture evolution in monsoonal Central Asia during the last 50,000 years

Quat. Sci. Rev.

A general cooling trend on the central Tibetan Plateau throughout the Holocene recorded by the Lake Zigetang pollen spectra

Quat. Int.

The influence of 14C reservoir age on interpretation of paleolimnological records from the Tibetan Plateau

Quat. Sci. Rev.

Environmental hydrochemistry of lakes and water system in Hoh Xil area, Qinghai province

Qinghai Environ.

Decadal- to centennial-scale climate changes over the last 2000 yr recorded from varved sediments of Lake Kusai, northern Qinghai-Tibetan Plateau

Quat. Res.

Encyclopedia of Rivers and Lakes in China: Section of River Basins in Northwest Region

Impact of hydrological conditions on the radiocarbon reservoir effect in lake sediment ¹⁴C dating: the case of Kusai Lake on the northern Qinghai-Tibet Plateau

Components of the ¹⁴C budget in Kusai Lake

The natural ¹⁴C contents of materials from hard-water lakes

Temporal changes of the ¹⁴C reservoir effect in lakes

The influence of ¹⁴C reservoir age on interpretation of paleolimnological records from the Tibetan Plateau